Stainless steels are usually welded by using filler metal compositions fundamentally the same as that of the base stainless steel. In accordance with certain welding operations, shrinkage of the weld upon cooling may cause distortion in the welded article. For example, 409 stainless steel filler metal is frequently used to weld stainless steel components together. 409SS solidifies as ferrite and remains ferrite during cooling to room temperature. As the 409SS material cools, it also shrinks thereby causing tensile residual stresses in the base metal components. These residual stresses can cause distortion in the part.
Residual stresses and the resulting distortion from the welded article can be particularly problematic in welding flanges to exhaust components for an exhaust system of an automobile. Flange flatness is particularly critical to insure that there is no leakage around the seals. If the flange is not flat enough due to distortion from shrinkage of the weld, leakage around the seals can cause emission failures. Efforts to prevent excessive warpage have been directed to the use of a thicker flange material which increases the cost and weight of the flange.
U.S. Patent Application Publication No. 2001/0030004 to Kushida et al. discloses a large-diameter, thick-wall martensitic stainless steel welded pipe for conveying crude oil or natural gas. The base metal is a stainless steel having a full martensite phase or a martensite phase as the main constituent with a ferrite phase contained therein and a seam weld metal which is stainless steel having a martensite phase as the main constituent with an austenite phase contained therein. The large diameter, thick wall pipe is not susceptible to distortion from shrinkage of the weld.
Accordingly, there is a need to provide a welded article that is less susceptible to residual stress and distortion without significantly increasing the cost or weight of the welded article. More specifically, there is a need for a weld filler metal that reduces residual stress and distortion in the weld joint of a welded article.